INDUSI'RIAI, A N D ENGINEEE'ING Cf3EMISTEY
November, 1927
and when the pressure wave reflected from the gallery walls passes through the gases they are again raised to the eomhustion temperature. The path of this wave and its speed are shown in Figure 2,B, beginning at a time near 3 milliseconds. It is nioving at a s p e d of around 750 meters a second. There is evidently an actual compression of the reacting gases as evidenced by the narrower width of the flame at a point around 4 milliseconds. There is then another exDansion which reaches its fullest &tent at about 5.8 milliseconds. During this expansion the reaction of the gases is again diminished, as shown by the dark area in the photograph. The compression which again follows acrrl~ratesthe reaction. 0 05 f Figure 2,C shows an interestinE Distance. meters nhot&ranh of a similar shot fired w u r e 4- 1 5 0 - G r s m Into tce 'gallery when it contained Charge of Petml8aible Ex"tneius ~ i . ~ r. a. nl. m.. ...~ ~ t -.. ~ onlv t ~air. . The ~ ~gases from this exGas plosive contain considerable quanti2!: 2: ties of carbon monoxide and hydrogen, and they are ignited in an "after-flame" similar in characteristics to the ignition taking place when the gallery contains gas. When the cannon is fired into the open air, where unlimited facilities for expansion exist, au after-flame is also produced, hut the compressions and rarefactions noticed in the gallery photographs do not take place. The photographs Figures 2,B and 3,B have h e n trimmed by making use of the data for position of flame from Figures 2,.4 arid 3,A so that the edge of the print represents approximately the position of the gallery walls with respect to the flame. It is evident that, when the camera faces the end of the gallery, a given lateral distance at the far end of the gallery or cannon end will produce a smaller image on the film than the same distance at the near end or diaphragm end. Hence, as the flame movm toward the camera the position of the gallery walls a t the flame front moves outward.
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The dark lines in Figures 2,B aiid 3,B are opaque pieces of paper pasted across the cellophane slot in the diaphragm. Disappearance of these dark lines indicates the breaking of the diaphragm. Photographic Results of l5O-Gram Charge Figure 3 shows similar photographs with a 150-gram charge of the same explosive. The flame from the explosive is projected a distance of 1.5 meters and has a total duration of about 1.5 milliseconds. There is then an interval or lag of about 1 millisecond when little flame is evident, after which flame appears in the fifth window and is propagated along the gallery a t a speed around 700 meters a second to the ninth window, after which it progresses no farther because of the heginning of a lateral expansion of the gases, as shown in Figure 3,B. There is evidence of a second and third similar phenomenon, after which the flame is propagated along the gallery at a slowly accelerating speed averaging ahout 130 meters a second. The bright areas which appear periodically at the firat windows may he the result of pressure wave8 reflected from the diaphragm, hut are more probably caused by the alternate compressions and expansion8 indicated in Figures 2,B and 3,B which tend to force the gases back toward the cannon as well as ahead toward the diaphragm end of the gallery. These are the subject of further study. Figure 4 shows a charge of I50 grams of a permissible explosive which did not cause a gas ignition. A future paper will give detailed results of shots of permissible explosives of various degrees of safety, fired both with and without stemming, into mixtures of gas and air and coal dust and air, and will endeavor to show the meaning of these ignition pictures in terms of the relative safety of the explosives. Acknowledgment
Thanks are due J. E. Tiffany, explosives engineer of this Station, who designed the gallery and moving film camera.
Improved Micro-Kjeldahl Ammonia Distillation Apparatus' By George Kemrnerer and L. T. Hallett Tim i:mv~$rsiru 01 I~ISCOXSIN, hlnnisou, WIS.
N STUDYIKG the fertilizers present iii lake water the Kjeldahl nitrogen was determined in t.he field, using samples that had been stored for only a few hours. The difficulty of transporting arid using the regular Kjeldahl apparatiis iii t,he field suggested the determination of the Kjolduhl nitrogen in the residues obtained hy the evaporation of the lake water. Since most of the lakes of northern 1%consin contain soft Knter, the small residues obtained ilcmandad a micro method.
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Preparation of Samples
Samples uf the water residues obtained by evaporating several liters of the lake water a t 80" (:. were dried at the same temperature. The dried material was then removed from the porcelain eraporating dish, usiiig great care to remove the last traces. These samples were then weighed as a whole and stored in small homeopathic vials. 1
Kcceircd
Jliiic
13, 1027
Usiug a micro balance, l0-mg. samples uf this residue were weiglied on small cover glasses riiadc by cutting the ends from test lubes. Each cover glass and sample was then placed in a small Pyrex digestion tube, and 2 cc. of sulfuric acid, 0.,5 gram of potassium sulfate. and a small crystal of copper sulfate were added to each digestion tube and tlre samples digest,eil over micro buriierfi mtil practically colorless. which required from 1 to 2 hours. The amnioiiia was then distilled horn tlie snmplcs. The cover gl helixd to premmt humpiiig during digestion. Divtillatiuri
The preliminary work WRS carried out with a distillation apparatus designed by Parnas and Wagner and recommended by l'regl.s The results were accurate and agreed well with the Kjoldahl determination carried out on the original water. The apparatus, however, has several rubber connections which soften very quickly when in contact with steam and 8
"Q,,antil&tive Oreanic Micrornslysis." 13. 97,irandhted by Pyiemnn.
Vol. 19,No. 11
INDUSTRIAL AND ENGIYEERING CHEMISTRY
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hot alkali, and much of the steam produced in the boiling chamber condenses before it reaches the distillation flask. The apparatus illustrated was designed to prevent the condensation of steam and make it possible to attach it to a single ringstand. It is built entirely of Pyrex, eliminating all rubber connections. The steam generator, A , is made from a 500-cc. Kjeldahl flask sealed to the chamber E , with openings a t L and K to allow the steam t o pass through B , E , F , and M to the distilling flask, N . Ammonia-free water is added t o A through the funnel D and a blank run to make sure that the water or apparatus does not contain ammonia. The digested sample and an r
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Pregl3 recommends distillation of the ammonia into N/70 hydrochloric acid and titration of the excess with N/70 sodium hydroxide, using methyl red as an indicator. In order to prevent solution of the alkali from the condenser tube by t h e distillate he substituted a silica tube, which is easily broken. With a Pyrex tube in the condenser no appreciable error due to the solution of the glass by the distillate has been detected. Results that equal those found by nesslerization were obtained by collecting the distillate in an excess of N/100 sulfuric acid and titrating back with N/100 sodium hydroxide using methyl red as indicator. Where the sample contains a large amount of nitrogen the titration is preferable t o nesslerization. Results
The results in Table I indicate the accuracy of the apparatus and method as used on samples of ammonium chloride. Table I1 shows typical results of over three hundred determinations carried out on lake-water residues, as obtained by Mr. Rex Robinson. Table I-Xitrogen i n Samples of Ammonium Chloride XITROGEN P~ITROGEN INTRODUCED OBTAINED ME. Mg. 0.067 0.070 0.070 0.070 0.070 0.070 0.070 0.071 0.068 0.070
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Table 11-Nitrogen i n Lake Residues WEIGHT O F NITROGEN SAMPLE SAMPLE OBTAINED Mg. Mg.ber liter 1 10.24 0.301 9.79 0.303 2 10.04 0.309 10.69 0.305 3 10.48 0.734 9.68 0.733 4 10.66 0.533 9.7s 0.523
@ p . cit., p . 97
Color Standards for Bone-Black Revivification Tests’ By Rene Baus
excess of potassium hydroxide are added to N through the funnel P. A trace of copper sulfate in the digested sample indicates when an excess of alkali has been added, The distillation is carried out with the stopcocks on the apparatus in the position indicated in the drawing. The condenser, T , is supplied with running water and small burners are placed under A and N . The steam generated in A passes to N , helps to liberate and carry the ammonia and steam through the tube H , and on passing through T is condensed and collected in a 50-cc. graduated flask containing 25 cc. of ammonia-free water. The condenser tube is placed below the surface of the liquid and 25 cc. of distillate are collected. The apparatus is prepared for the next sample by removing the burners and allowing the solution in N to be drawn into chamber E by the vacuum caused by the condensation of the steam. A small depression a t the bottom of flask N facilitates complete removal of the distilled sample. The distillation flask is rinsed by placing a burner under A and turning the three-way stopcock to connect C with LM. When sufficient water has siphoned in N , the stopcock is turned as in the illustration, the flame removed, and the rinse water sucked back into E as before. The tube S,t o which is attached a rubber tube closed with a pinchcock, is now opened and the used sample flows out. The apparatus is now ready for a second determination. Five minutes are required for a complete distillation. Nitrogen Determination
An aliquot of the distillate, usually one-half, is diluted to 50 cc. in a Nessler tube, nesslerized, and compared with standards treated similarly and a t the same temperature.
GRAMERCY, LA.
E caustic soda test for thoroughness of char reviviTHfication has been used in sugar-refining for many years and has proved of great value in the control of kiln work. Good practice in making this test is to boil 60 grams (measured) of char with 75 ml. of 9 ” Brix caustic soda solution for 2 minutes in a covered 250-ml. copper beaker and then filter through paper or cotton into a test tube. The quality of revivification is judged from the color imparted to the caustic solution by organic matter which has not been thoroughly carbonized in the kiln. Absence of color indicates over-burning, well-burnt char gives only a faint lemon yellow, and any tendency towards a brown color indicates poor burning. A set of color standards for reference has value where several persons in a plant-as the control chemist, shift superintendent, and the charhouse foreman-are each guided by the results of the tests. Standards closely matching the yellow to brown color tone of the test and which are easily duplicated can be prepared from acidified solutions of the bromthymol blue dye which is used for p H work. Four standards, graded “orerburnt,” “ i d 1 burnt,” “mediocre,” and “poor” are sufficient for kiln control. These can be made up in the order given by adding to 35-ml, portions of 0.5 per cent acetic acid 0.25, 0.50, 1.0, and 2.0 ml. of 0.04 per cent bromthymol blue. This gives enough solution to fill the 175 by 20-mm. test tube used for comparisons, The standards will not fade for several weeks if tightly corked and sealed with paraffin. 1 Received
September 12, 1927.
